Hard metal alloy



Reissued July 30, 1940 UNITED STATES PATENT OFFICE man METAL ALLOY,ESPECIALLY roa TOOLS Paul Schwarzkopf, New York, N. Y., assignmto TheAmerican Cutting Alloys, Inc., New York. N. Y., a corporation ofDelaware No Drawing. Orlm'mal No. 2,122,157, dated June 2a, 1938, SerialNo. 743,717, September 12, 1934. Application for reissue February28,1940, Serial 18 Claims.

27, 1932 and issued into Patent No. 2,091,017,

which in turn was copending with my applicationsSer. No. 656,103, filedFebruary 10, 1933 and issued into Patent No. 1,959,879, and Ser. No.452,132, filed May 13, 1930.

It is an object of the invention to increase the hardness and toughnessof such hard metal alloys.

It is another object of the invention to make such hard metal alloysapplicable to uses both known so far and new ones. I

It is another object of the invention to increase the resistance of suchherd metal tool alloys against mechanical wear and chemical eiTects,

such as oxidation, of the surrounding air or moisture, or .a coolingliquid, such as water.

It is a further object" of the invention to increase the hardness of thealloy without impairing its toughness and the size of particlescontained therein. I

It'is still another object of the invention to increase the speed atwhich hard alloys of this kind' can be used for cutting, drilling,milling, and other machining purposes. 1

These and other objects of the invention will be more clearly understoodas the specification proceeds.

According to the prior art, hardmetal alloys had to be made and storedin different grades depending upon the intended use. So, for instance, acertain grade was usable for machining steel, another grade for workingsemi-steel and a third grade for machining cast iron. Within the gradesthemselves diflerentiations have been established depending upon thecomposition of the material tobe worked. The grades usable for workingsteel or cast iron could not be used for successfully working glass, orartificial resins, and the great number of grades made the proper andsimple handling of them in the manufacture as well as in thedistribution very difficult.

According to the invention, a hard metal alloy can be obtained beingusable for several purposes. 80, for instance, the same hard metal alloycan be used for machining steel and cast iron.

In my Patent 1,959,879 I suggested a method of manufacturing a hardmetalalloy containing mixed crystals,i. e. solidsolutions of two or morecarbides of elements selected from the third,

fourth, fifth, and sixth group of the periodical system, cemented bylower melting auxiliary metal substantially taken from the iron group,and I do not claim that process in the present application.

The present invention concerns a hard composition for tool elements andother working appliances consisting substantially of three or more hardand refractory carbides of different elements selected from the third,fourth, fifth, and sixth group of the, periodical system and auxiliarymetal substantially ofthe .eight group of the periodical system inamounts from about 3% to 25% by weight and wherein substantial amounts.of said carbides form mixed crystals, i. e. crystalline solid solutionsor homogeneous carbide crystal structures each of which contains atomsof diflerent selected elements besides, of course,

atoms of carbon necessary to form carbide with thoseselected elements.

As is well known in the art .and established 'by experiments andscience, solid solutions of two or more substances result in a compoundthe hardness of which exceeds that of either component substance.Therefore, the present invention consists particularly in a hardcomposition for the uses pointedoutabove, composed substantially ofthree or more hard and refractory carbides of diflerent elementsselected from the third through sixth group of the periodical system andauxiliary metal substantially of the eighth group of the periodicalsystem, preferably of the iron group, in amounts from about 3% to 25% byweight, in which at least a substantial amount of the carbides arecompounded to form mixed crystals or homogeneous carbide crystalstructures as defined above, 1. e. solid solutions the hardness of whichexceeds that of either carbide combined in the solid solutions orhomogeneous carbide crystal structures.

Although it is possible to manufacture a hard composition according tothe invention in a process as disclosed and claimed in my Patent1,959,879, it has been experienced that it is sometimes diflicult tocompound three or more carbides into solid solutions in substantialamount and to secure uniform distribution of all constituent carbidesthroughout the body of the composition.

According to a feature of this invention one can successfully proceed inmanufacturing such mixed crystals or solid solutions by first forming atleast two pairs of. solid solutions, each consisting of two selectedcarbides, and thereafter combining those pairs of difierent compositionsI as to carbides contained, into a new mixed crystal. Taking forinstance a mixed crystal consisting of tungsten carbide and molybdenumcarbide, and another mixed crystal consisting of molybdenum carbide andtitanium carbide, and combining them to form a new mixed crystal, itwill contain the three components tungsten carbide, molybdenum carbide,and titanium carbide, and thereby two "binary mixed crystals have beentransformed into a "ternary" mixed crystal. In the same way a binarymixed crystal consisting of tungsten carbide and tantalum carbide, andanother binary mixed crystal consisting of molybdenum carbide andtitanium carbide, can be combined to a single mixed crystal whichcontains, however, four components, namely tungsten carbide, tantalumcarbide, molybdenum carbide, and titanium carbide, and forms aquatemary" mixed crystal. The mixed crystals so obtained may then bepowdered to any desired degreeand mixed with one or more auxiliarymetals as for instance cobalt, iron, nickel. The mixture so obtained isthen heated till at least part of the auxiliary metal is molten wherebysometimes part of the mixed crystals may be dissolved in the auxiliarymetal. Thereupon the mixture is cooled. During cooling some the amountof mixed crystals added to the mixture before heating must be sufiicientin order to secure the wanted amount of mixed crystals in the solidifiedbody after cooling. The amount of carbide being known which may bedissolved, if at all, in a certain quantity of auxiliary metal present,if being heated to a certain temperature and that temperature beingmaintained for a certain time, also the percentage being known of mixedcrystals dissolved which will -be precipitated again during cooling ofthe auxiliary metal forming'the solvent for the mixed crystal, it iseasyfor any one skilled in the art, to determine in advance the amount ofmixed crystals to be formed and added to ,a hard metal mixture accordingto the invention for securing quantitatively and qualitatively theamount and composition of mixed crystals present in the finished body.So, for instance, ii knowing the mixed crystals used are soluble in anauxiliary metal present at the temperature of sintering, one may add tothe mixture a surplus of such mixed crystals to such extent that thesurplus covers the exact amount of mixed crystals dissolved in theheated auxiliary metal and not being precipitated again while cooling.Or, by using certain auxiliary metals not dissolving a certain mixedcrystal or, by observing a certain law of heating the mixture or, byavoiding a certain excessive temperature, or by following two or more ofthese rules, any wanted composition of the finished body can beobtained.

There exist several ways of explaining the surprising result of theinvention, although the inventor declines to limit the invention or tobase it on any theory.

According to the theory applying to mixed crystals or solid solutions,as referred to above and in my copending applications, particularly myPatent 1,959,879, the hardness of mixed crystals or solid solutionsexceeds that of either component substance, and consequently thehardness of solid solutionsformed of. three or more carbides exceedsthat of either component carbide.

While in the above patent I have described a particular method ofmanufacturing hard metal tool alloys comprising three or more hard andrefractory carbides, it should be understood that any other method asdisclosed in my earlier applications may be applied.

Thus the three or more metals selected to form the desired carbidecompounds, or even their oxides may be admixed with carbon in sufilcientamount to form the desired carbide, and if oxides were introduced, toreduce the latter to their metallic state and thereafter carbidize them.The mixture preferably powdered as finely as possible is heated tosintering or melting temperature, and a hard composition obtainedthereby in which the desired carbide compounds and homogeneous carbidecrystal structures as defined above are present. The hard composition isthen ground, if necessary,

,to desired particle size, admixed with powdery auxiliary metal, shapedand sintered preferably between 1330 to 1600 C. for e. g. one to fourhours 11'. metal of the iron group is used as auxiliary metal.

Moreover, the three or more metals, or even their oxides, selected toform the desired carbide compounds may be admixed, on one hand, withcarbon in sufllcient amount so as to ca'rbidize the elements or oxides,,and, on the other hand, with the selected auxiliary metal, and themixture preferably powdered as finely as possible, heated to sinteringtemperature for a suflicient period of time so that a tough-and hardcomposition results containing the desired compounds, including solidsolutions or homogeneous carbide crystal structures as defined above,cemented by the auxiliary metal. Furthermore, three or more selectedcarbides may be admixed with the selected auxiliary metal in as finelydivided state as possible, and heated to sintering temperature for asufllcient period of time so that a cemented hard composition results,containing solid solutions or homo- .geneous carbide crystal structuresas defined above, of the carbides in substantial amount.

If metal oi the iron, group is used as auxiliary metal, heating tobetween about 1330 to 1600" C.'for e. g. one to four hours is advisable.

However, any other method of'manufacturing the hard and toughcomposition answering the invention may be used.

It is sometimes diflicult to compound certain carbides in desired ratioto form a solid solution. Thus, it is sometimes diflicult to incorporatethe very important titanium carbide in the desired other hard carbide,in extraordinarily uniform distribution.' By the'addition of a thirdcarbide, such as molybdenum carbide, even in small amounts as shownhereafter, such incorporation and distribution of all the constituentcarbides and their mutual thorough permeation can readily andeconomically be secured.

It is not necessary, according to the invention, that the hard metalalloy contains solely at least ternary mixed crystals as far as thecarbides present are concerned. It is satisfactory, however, for theinvention if only substantial amounts of such mixed crystals arepresent. According to experience already about 10% of the hardmetalalloy formed by at least ternary mixed crystals or homogeneouscarbide crystal structures as defined above, are capable of considerablyimproving the properties of the hard metal. If about half of thecarbides present or more are transformed into such ternary mixedcrystals, a decisive improvement can be ascertained. Besides, auxiliarymetal may be present in amounts of from about 3% to 25%. The amounts ofternary, quaternary, and so on, mixed crystals of carbide of elementstaken from the third, fourth, fifth, and/or sixth group of theperiodical system may conveniently amount to at least from about 35 to45% of the alloy, up to about 75% to 95% of it, the remainder beingformed by binary and/or simple carbide of the same or other ele-' mentstaken from the same or other groups of the periodical system, andauxiliary metal preferably taken from the eighth group of the periodicalsystem, and especially from the iron group, in amounts from about 3% toabout 25% by-weight of the alloy.

It is quite difficult to mention any minimum amounts of carbide to bepresent, because titanium carbide occupy a space four times as large as5% by weight of tungsten carbide. Nevertheless, the minimum amount ofcarbide to be present and forming part of a ternary, and

so on, mixed crystal according to the invention, has to be substantialand, as a minimum, about 1% by weight of the alloy. In manufacturingthealloy, the carbides are to be chosen so that they readily-form mixedcrystal pairs (binary mixed crystals) and that further, the mixedcrystals so obtained are capable of forming again lybdenum, tungsten.But alsoelements of'the.

eight group as chromium, cobalt, nickel, iron, may sometimes be chosento form carbides to be combined with those of other elements to formmixed crystals. These carbides have in common the properties of beingsumciently hard and refractory, i. e. they do not decompose under theinfluence of water and/or air at elevated temperatures. Hard metals areused in the first place as tool implements for high speed work. Therebythe temperature of the hard metal and at least of its working edge israised by several hundred centigrades and cooling water is to beapplied. Therefore among all carbides of elements belonging to the thirdto sixth group of the periodical system only those are suitable andconsequently to be chosen for the purposes of the invention which arerefractory in the sense just defined and which is meant also by the useof the term refractory in the appended claims.

In practice for instance the following alloy has prov'en to be mostadvantageous: About 60% to 75% tungsten carbide, in the form of W2C;about to 25% titanium carbide; about 1% to 25% molybdenum carbide; about5% to 25% cobalt, nickel and/or iron. In such a mixture titanium carbidemay particularly be present in amounts offrom about 12% to molybdenumcarbide in amounts of from about 1% to 5%- In manufacturing the hardmetal alloy, first two groups of mixed crystals are formed, one groupbide, titaniumcarbide, and molybdenum carbide.

The formation of mixed crystals may occur by heating the chosen amountsof the carbides up to from about 1600 to 2000 C., preferably in aneutral or carbon-containing atmosphere. the same way the ternary (andso on) mixed crystals can be obtained by heating the previously obtainedmixed crystals up to the same range of temperature; or a higher one, upto about 2600 C. The temperature to be-applied depends on the meltingtemperature of the carbides themselves, on their mutual solubility, andon the time of heating. If applying the heat within a range of about1600 to 2000" C., a heating of from 1 to 4 hours regularly sufflces. Themixed crystals so obtained are then powdered and mixed with theauxiliary metal preferably powdered to about the same degree and thensintering has to be done within a range of temperature of above 1300 C.up to about 1400 to 1600 C.

While any man skilled in the art can proceed to practice the inventiondescribed, there may be given, nevertheless, a few further examples ofmaking hard metal tool alloys according to the invention. I

The special tool alloy described hereinbefore and containing tungstencarbide, titanium carbide, molybdenum carbide, and auxiliary metal takenfrom the eighth group of the periodical system, may be manufactured inabout the following way: 5% by weight of M020 and 4% by weight of TiCare powdered, intimately mixed, preferably in a ball mill, for about to30 hours, and then heated up to about 1600 to 2000" C. in a crucible andpreferably byinduction for about one to two hours, whereby mixedcrystals of them are obtained. About 65% by weight of W2C and about 12%by weight of TiC are powdered preferably in a ball mill for about 20 to36 hours and then heated in the same way, up to about 1600- 2000 C. forone to four hours. Both kinds of mixed crystals so obtained are thenintimately mixed again and powdered preferably in a ball mill by.treating them for about 10 to 40 hours therein so that they are again asfinely divided as possible, and heated again up to about 1600- 2000 C.for about one to four hours. Thereby new mixed crystals are obtainedcomprising the two kinds of mixed crystals which have been in-' timatelymixed together before. To this mixture is then added auxiliary metal inamounts of about 14%, consisting for instance of 13% nickel and 1%chromium. This material is once more intimately mixed preferably in aball' mill by treating'it for about 4 to 24 hours therein, whereupon thepowder so obtained may be pressed about 8% TiC and 35% 'I'a'C, the othergroup of 8% TiC and 35% W20, this group of mixed cryscombined to formternary mixed crystals, to-

tals .being manufactured 'in an analogous way as described before in thebody of the specification, whereupon the two groups are intimately mixedand again heated up to about 1600 to 2000 C. or more, whereby new mixedcrystals of them are obtained. After adding auxiliary metal, the mixturemay be shaped and sintered.

Alsoa group of mixed crystalsmay be formed,

however, consisting of about 8% TiC and 10% M020, and another groupconsisting of 60% W20 and 15% MOaC, whereupon these two groups are whichare then added about 7% cobalt as auxiliary metal. This mixture is thenshaped and sintered. g V

Apparently, in the three examples the binary mixed crystals pertainingto the two groups to be combined subsequently, present a hardness whichis higher than that of the single carbides constituting the respectivemixed crystals, because the amounts of thecarbides to be combined in amixed crystal are chosen accordingly.

' the periodical system in an amount of about 3% to 25% by weight, and ahard and refractory crystalline carbide substance of at least threeelements selected from the third through sixth group. of-the periodicalsystem, a substantial amount of said carbide substance forming homo- 40geneous carbide crystal structures each containing atoms of differentselected elements, from said groups in addition to carbon atoms.

2. A cemented hard metal compomtion, for tool elements and other workingappliances, consist' 4 ing of at least three diflerent hard andrefractory carbides of elements selected from the third,

, fourth, ilfth and sixth group of the periodical system and auxiliarymetal substantially of the eighth group of the periodical system inamounts to of about 3% to about 25% by weight, substantial amounts ofsaid carbides forming solid solutions.

3. In a hard metalas being claimed in claim 1', the carbide substancepresent amounting from about 75% to 95% by weight 'of the final ody andforming homogeneous carbide crystal structures amounting 4. A hard metalas being claimed inclaim 1,

the auxiliary metal'being chosen from the eighth from about 35%;up to75% and do and sixth group of the periodical system".-

5. A hard metal as claimed in claim 1, containing carbide of at leastone element of the eighth group in substantial amount besides hard andrefractory carbide substance of elements of as, the third to sixth groupof the periodical system.

"' "6. A-hard metal as claimed in claim 1, containing carbide of atleast one element ofthe eighth group in amount from about 1% to 5%.

besideshard and refractory carbide substance of elements of the-third tosixth group of the periodical system.

'l. A hard metal composition as claimed in vclaim 2, the auxiliary metalbeing chosen from the eighth and sixth group of the periodical system.

a1,sao

8. A cemented hard metal composition sintered by heat treatment, fortool elements and other 'working appliances, consisting substantially ofat least three different hard and refractory carbides of elementsselected from the third through sixth group of the periodical system andauxiliary metal substantially of the eighth group of the periodicalsystem in amounts of about 3% to about 25% by weight, the minimum amountof a thereby to increase the average hardness of the carbide substancecontained in the composition.

9. A cemented hard metal composition sintered by heat treatment, fortool elements and other working appliances, consisting substantially ofat least three different hard and refractory carbides of elementsselected fromthe third through sixth group of the periodical system andauxiliary metal substantially of the eighth group of the periodicalsystem in amounts of about 3% to 25% by weight, a minimum amount of aselected carbide to be about one percent, said carbides pres ent infinely divided state and heat treated to form in substantial amounthomogeneous carbide crystal structures containing atoms of differentselected elements of said groups in addition to carbon atoms and therebyto increase the average hardness of the carbide substance contained inthe composition. s

10. A cemented hard metal composition sintered by heat treatment, fortool elements and other working appliances, consisting substantially ofat least three hard and refractory car-' bides of diflerent elementsselected from the third through sixth group of theperiodical system andauxiliary metal substantially of the iron group in amounts of about 3%to about 25% by weight, the minimum amount of a selected carbide to beabout one percent, said carbides being present in as finely divided astate as possible and heat treated to form solid solutions insubstantial amount and thereby to increase the average hardness of. thecarbide substance contained in the composition. I

11. A cemented hard metal composition sintered by heat treatment, fortool elements and other working appliances, consisting substantially ofcarbide substance and auxiliary metal substantially of the iron group inamounts of selected carbide to be about one percent, said carbides heattreated to. form in substantial amount homogeneous carbide crystalstructures containing atoms of diiferent elements from said groups inaddition to carbon atoms and thereby to increase the average hardness ofsaid carbide substance.

, A l 12. A sintered hard metal composition for tool elements and otherworking appliances, substantially consisting of at least threediil'erent carbides selected from a group of carbides of the elementsmolybdenum, tungsten, titanium, tan lum. boron, vanadium, columbium, andauxiliary metalfsubstantially of the eighth group oiHzhe periodicalsystem in amounts of about 3% to about 25% by weight, the minimum amountof a selected carbide to be about one percent, and 1 titanium, tantalum,tungsten, and auxiliary metal substantially of the iron group in amountsof about 3% to about 25% by weight, the minimum amount of a selectedcarbide to be about one percent, and substantial amounts of saidcarbides forming homogeneous carbide crystal structures containing atomsof different'ones of said elements in addition to carbon atoms.

14. A sintered hard metal composition, for tool elements and otherworking appliances, consisting substantially of carbides of the elementsmolybdenum, tantalum, titanium, and auxiliary metal substantially of theiron group in amounts of about 3% to about 25% by weight, the minimumamount of a selected carbide to be about one percent, and substantialamounts of said carbides forming homogeneous carbide crystal structurescontaining atoms of different ones of said elements in addition tocarbon atoms.

15. In a method of producing a hard metal for tool elements and otherworking appliances containing at least three hard and refractorycarbides of elements selected from the third, fourth, fifth, and sixthgroup of the periodical system, and auxiliary metal substantially of theeighth group of the periodical system in amounts from about 3% to 25%,transforming substantial amounts of said carbides into at least twogroups of mixed crystals, each group containing different carbides,mixing substantial amounts of mixed crystals of said groups andforming'from this mixture newly combined mixed crystals, andconsolidating the mass so obtained with the auxiliary metal by treatmentat elevated temperatures up to about 1400" to 1600 C.

16. In a method of producing a hard metal for tool elements and otherworking appliances containing at least three'hard and refractorycarbides of elements selected from the third, fourth, fifth, and sixthgroup of the periodical system,

and auxiliary metal substantially of the eighth group of the periodicalsystem in amounts from about 3% to 25%, transforming by heat treatmentat above about 1600 C. substantial amounts of said carbides into atleast two groups of mixed crystals, each group containing differentcarbides, mixing substantial amounts of mixed crystals of said groupsand forming from this mixture newly combined mixed crystals by heattreatment at above about 1600 C., and consolidating the mass so obtainedwith the auxiliary metalby treatment at elevated temperatures up toabout 1400 to 1600 C.

17..In a method of producing hard metal for tool elements and otherworking appliances containing at least three hard and refractorycarbides of elements selected from the third, fourth, fifth and sixthgroup of the periodical system and auxiliary metal substantially of theeighth group of the periodical system in amounts from about 3% to 25%,transforming substantial amounts of said carbides into at least twogroups of mixed crystals, each group containing different car-.

bides, mixing substantial amounts of mixed crystals of said groups andforming from this mixture newly combined mixed crystals, adding theretoa substantial amount of at least one of said carbides and auxiliarymetal, and consolidating the mass so obtained by treatment at elevatedtemperatures up to about 1400 to 1600 C.

18. In a method of producing hard metal for tool elements and otherworking appliances containing at least three hard and refractorycarbides of elements selected from the third, fourth, fifth and sixthgroup of the periodical system and auxiliary metal substantially of theeighth group of the periodical system in amounts from about 3% amountsof said carbides into at least two groups of mixed crystals, each groupcontaining different carbides, mixing substantial amounts of mixedcrystals of said groups and forming from this mixture newly combinedmixed crystals by heat treatment at above about 1600 0., adding theretoa substantial amount of at least one of said carbides and auxiliarymetal, and consolidating the mass so obtained by treatment at elevatedtemperatures up to about 1400 to 1600 C.

PAUL SCHWARZKOPF.

to 25%, transforming substantial-

